RUI: Novel Heavy Element Transition Metal Oxides; Low Dimensional Magnetism vs. Geometric Magnetic Frustration

RUI：新型重元素过渡金属氧化物；

• 批准号: 1601811
• 负责人: Shahab Derakhshan
• 金额: $ 29.98万
• 依托单位: California State University-Long Beach Foundation
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-07-01 至 2020-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1601811&HistoricalAwards=false
• 关键词: RUI; Novel; Heavy; Element; Transition

NON-TECHNICAL SUMMARY:Magnetic materials have been the subjects of scholarly research for many years. This project will focus on the investigation of a particular class of magnetic systems having triangular arrangements of magnetic ions, which display unusual and little-investigated behavior. The proposed parent materials will also be subjected to chemical modification, and the resulting systems will provide a great opportunity to elucidate the role of crystal symmetry and quantum aspects on determination of the resultant magnetism. A major focus will also be devoted to synthesis of magnetic materials and study of the effects of geometrical and low-dimensional structural contributions. Some of these systems are particularly important as they are expected to exhibit interesting electronic transport properties.The interdisciplinary nature of the project is attractive from an educational perspective for many scientific communities, i.e. chemistry, physics, electronics, materials, etc. Undergraduate and graduate students will be exposed to a large variety of synthetic methods, characterization techniques, and physical properties measurements in the field of solid-state materials chemistry. Some of the research will be conducted in national laboratories, offering valuable opportunities for students to collaborate with other scientists and benefit from hands-on research experience in world-class research facilities. Also, magnetism and magnetic materials are at the basis of many components of daily human life (electric motors, data storage devices, medical imaging technologies, etc.) and this project will advance public awareness of the field of magnetic materials. It will also include development of new courses and programs, attracting students to pursue academic studies in STEM fields, organizing outreach programs in local high schools, and presenting results at scientific conferences. TECHNICAL SUMMARY:In antiferromagnetic (AFM) materials with triangular arrangements of magnetic ions, all the spin constraints cannot be satisfied simultaneously and conventional static magnetic ordering is inhibited. This results in a phenomenon, which is known as geometric magnetic frustration (GMF) where exotic ground states with enormous degeneracies are present. Nonetheless, this condition may be violated when the exchange interactions of different strengths lift the degeneracy and the dominating interaction results in low dimensional magnetism (LDM). This project aims to develop a profound insight into both structural and electronic variables that determine the criteria for the two above-mentioned regimes, LDM vs. GFM. The goals will be achieved by exploratory syntheses, characterizations, and physical properties measurements of rationally designed materials. These will include novel 4d and 5d transition metal oxides in ordered NaCl structure type or in B-site ordered double perovskite structure type, which are composed of triangular magnetic sub-structure. Moreover, the successfully synthesized and characterized parent compounds will undergo further systematic chemical modifications, by which the oxidation states of magnetic ions and/or structural features will be altered. This in turn, will change the degree of frustration and will enable understanding of the interplay between the variables and the ground state magnetic structure. An essential component of the program is the high level of undergraduate and M.S.-level graduate students' participation, particularly those from underrepresented groups, in the societally important area of materials science.

非技术综述：磁性材料多年来一直是学术研究的主题。这个项目将集中于研究一类特殊的磁性系统，这些系统具有磁性离子的三角形排列，表现出不寻常的和很少被研究的行为。提出的母体材料也将受到化学修饰，由此产生的系统将提供一个很好的机会来阐明晶体对称性和量子方面在确定合成磁性方面的作用。重点还将放在磁性材料的合成以及几何和低维结构贡献的影响的研究上。其中一些系统特别重要，因为它们有望显示出有趣的电子传输性质。从教育角度来看，该项目的跨学科性质对许多科学界具有吸引力，如化学、物理、电子学、材料等。本科生和研究生将接触到固态材料化学领域的各种合成方法、表征技术和物理性质测量。其中一些研究将在国家实验室进行，为学生提供宝贵的机会与其他科学家合作，并受益于在世界级研究设施中的实践研究经验。此外，磁性和磁性材料是人类日常生活许多组件(电动马达、数据存储设备、医学成像技术等)的基础。该项目将提高公众对磁性材料领域的认识。它还将包括开发新的课程和项目，吸引学生在STEM领域进行学术研究，在当地高中组织外展计划，以及在科学会议上展示成果。技术综述：在磁性离子呈三角形排列的反铁磁(AFM)材料中，所有的自旋约束都不能同时满足，从而抑制了传统的静态磁有序。这导致了一种被称为几何磁阻(GMF)的现象，其中存在具有巨大简并的奇异基态。然而，当不同强度的交换相互作用解除简并，并且主要相互作用导致低维磁性(LDM)时，这一条件可能被违反。本项目旨在深入了解决定上述两种制度标准的结构变量和电子变量，即LDM与GFM。这些目标将通过合理设计的材料的探索性合成、表征和物理性能测量来实现。这将包括新型的4d和5d过渡金属氧化物，它们是由三角形磁性亚结构组成的有序氯化钠结构类型或B位有序双钙钛矿结构类型。此外，成功合成和表征的母体化合物还将经过进一步的系统化学修饰，从而改变磁性离子的氧化状态和/或结构特征。这反过来将改变受挫的程度，并将使人们能够理解变量和基态磁结构之间的相互作用。该项目的一个重要组成部分是高水平的本科生和硕士研究生的参与，特别是那些来自代表人数较少的群体的学生，他们参与了具有社会重要性的材料科学领域。